Teaching Case

A 17-year-old female patient presented to the emergency department during the night with sudden abdominal pain localised to the hypogastrium. The urine analysis was normal, and she didn’t have fever, vomits or diarrhoea. Since at that time ultrasonography was not available, computed tomography (CT) was requested.

Unenhanced CT showed a solid mass in the midline, posterior to the bladder, which was interpreted as a haemorrhagic cyst, and a small amount of free fluid in the pelvic cavity (Fig.1).
Ultrasound demonstrated a 9 cm solid, hypoechogenic mass, localised to the hypogastrium (Fig. 2), but its origin wasn't clear and the left ovary couldn’t be individualised, so Magnetic Resonance Imaging (MRI) was performed.
MRI showed the tumour arising from the left ovary, associated with an ipsilateral amorphous tubular mass-like structure (corresponding to the thickened Fallopian tube), and uterine deviation to the left side (Fig. 3). The left ovary was compressed, with increased signal intensity on T2WI (Fig. 4) and showing poor enhancement after gadolinium, especially when compared to the right (Fig. 5). There was also engorgement of the ipsilateral vessels around the tube (Fig. 6). The underlying mass was markedly hypointense both on T2WI and T1WI, enhancing homogeneously and gradually after gadolinium administration (Fig. 7).

Adnexal torsion is a gynaecologic emergency caused by partial or complete twisting of the mesovarium. It is an infrequent cause of acute lower abdominal pain, occurring more frequently in young children due to hypermobility of the ovary. In adulthood, there is usually an underlying ovarian lesion causing adnexal torsion, most frequently mature teratoma [1].
Imaging is essential for the diagnosis since the clinical findings aren’t specific and early surgical intervention is needed [2].
The sonographic findings are variable and closely related to the duration, degree of torsion and the presence or absence of an associated intra-ovarian mass or haemorrhage. The most constant finding is ovarian enlargement, usually associated with multiple small uniform cysts aligned in the periphery. Free pelvic fluid in the cul-de-sac can also be seen. The identification of a whirlpool sign on Doppler ultrasound, despite being pathognomonic of adnexal torsion, is uncommonly seen. Doppler has in fact a limited role in the diagnosis of ovarian torsion, since normal blood flow is frequently seen in torsed adnexa [3].
CT is usually performed when there is suspicion of pelvic inflammatory disease. In the context of ovarian torsion it can show tubal thickening, a pelvic mass, ascites, and uterine deviation to the twisted side [3].
MRI isn’t frequently performed for diagnosing ovarian torsion, but it can show an enlarged and oedematous ovary, with increased signal intensity from the stroma on T2 WI, as well as peripheral distributed follicles. Other findings include ascites and uterine deviation to the twisted side. An abnormally contrast-enhanced ovary is suggestive of torsion, however, the presence of a normal enhancement does not exclude the diagnosis [2].
MRI also offers characterisation of the ovarian mass underlying the torsion, allowing its definitive diagnosis [2].
Fibromas are benign ovarian tumours composed of fibrous tissue, and rarely can they be responsible for ovarian torsion. CT shows a homogeneous solid tumour with delayed enhancement [4]. Because of their abundant collagen contents, these tumours have low signal intensity on T1WI and very low signal intensity on T2WI [5]. On post-contrast T1FS, mild and usually homogeneous enhancement is seen [6].
Emergency surgery is usually the treatment of choice in ovarian torsion. Most ovaries are already necrotic at the time of diagnosis, with the ulterior risk of infection leading to abscess formation or peritonitis, and require salpingo-oophorectomy. In the case of a non-infarcted adnexa, surgical untwisting can be performed [2].
In our case, the patient was treated surgically, which confirmed the diagnosis.